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LM34919 Dataheets PDF



Part Number LM34919
Manufacturers National Semiconductor
Logo National Semiconductor
Description 600mA Constant On-Time Buck Switching Regulator
Datasheet LM34919 DatasheetLM34919 Datasheet (PDF)

LM34919 Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator June 2, 2008 LM34919 Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator General Description The LM34919 Step Down Switching Regulator features all of the functions needed to implement a low cost, efficient, buck bias regulator capable of supplying 0.6A to the load. This buck regulator contains an N-Channel Buck Switch, and is available in a micro SMD package. The constant on-time feedback regulation schem.

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LM34919 Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator June 2, 2008 LM34919 Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator General Description The LM34919 Step Down Switching Regulator features all of the functions needed to implement a low cost, efficient, buck bias regulator capable of supplying 0.6A to the load. This buck regulator contains an N-Channel Buck Switch, and is available in a micro SMD package. The constant on-time feedback regulation scheme requires no loop compensation, results in fast load transient response, and simplifies circuit implementation. The operating frequency remains constant with line and load variations due to the inverse relationship between the input voltage and the on-time. The valley current limit results in a smooth transition from constant voltage to constant current mode when current limit is detected, reducing the frequency and output voltage, without the use of foldback. Additional features include: VCC under-voltage lockout, thermal shutdown, gate drive under-voltage lockout, and maximum duty cycle limiter. Features ■ Integrated N-Channel buck switch ■ Integrated start-up regulator ■ Input Voltage Range: 8V to 40V ■ No loop compensation required ■ Ultra-Fast transient response ■ Operating frequency remains constant with load current and input voltage ■ Maximum switching frequency: 2.0 MHz ■ Maximum Duty Cycle Limited During Start-Up ■ Adjustable output voltage ■ Valley Current Limit At 0.64A ■ Precision internal reference ■ Low bias current ■ Highly efficient operation ■ Thermal shutdown Typical Applications ■ High Efficiency Point-Of-Load (POL) Regulator ■ Non-Isolated Telecommunication Buck Regulator ■ Secondary High Voltage Post Regulator Package ■ micro SMD Basic Step Down Regulator © 2008 National Semiconductor Corporation 300044 30004431 www.national.com LM34919 Connection Diagrams Bump Side 30004402 Top View 30004433 Ordering Information Order Number LM34919TL LM34919TLX Package Type 10-Bump micro SMD 10-Bump micro SMD NSC Package Drawing TLP10A1A TLP10A1A Junction Temperature Range −40°C to + 125°C −40°C to + 125°C Supplied As 250 Units on Tape and Reel 3000 Units on Tape and Reel www.national.com 2 LM34919 Pin Descriptions Pin Number A1 Name RON/SD Description On-time control and shutdown A2 RTN Circuit Ground A3 FB Feedback input from the regulated output B1 SGND Sense Ground B3 SS Softstart C1 ISEN Current sense C3 VCC Output from the startup regulator D1 VIN Input supply voltage D2 SW Switching Node D3 BST Boost pin for bootstrap capacitor Application Information An external resistor from VIN to this pin sets the buck switch on-time. Grounding this pin shuts down the regulator. Ground for all internal circuitry other than the current limit detection. Internally connected to the regulation and over-voltage comparators. The regulation level is 2.5V. Re-circulating current flows into this pin to the current sense resi.


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